Vehicle sound effect generation apparatus

ABSTRACT

A vehicle sound effect generation apparatus includes a running state detecting unit that detects a running state of a vehicle, an adjustment wave sound selector that selects one or more adjustment wave sounds having a half-order frequency component or an integer-order frequency component, a sound effect generation unit that synthesizes a fundamental wave sound having a fundamental frequency component with the one or more adjustment wave sounds selected by the adjustment wave sound selector, and an inhibition condition determining unit that can determine a condition that correspondence between an amount of an operation performed by a vehicle occupant and a behavior of the vehicle is inhibited. When the inhibition condition determining unit determines the condition that the correspondence between the amount of the operation and the behavior of the vehicle is inhibited, the adjustment wave sound selector reduces the output characteristics of the adjustment wave sounds selected.

TECHNICAL FIELD

The present invention relates to a vehicle sound effect generationapparatus and particularly relates to a vehicle sound effect generationapparatus that controls output characteristics of a sound effect basedon an inhibition condition such that correspondence between an amount ofan operation performed by a vehicle occupant and a vehicle behavior isinhibited.

BACKGROUND ART

In recent years, in-vehicle silencing is being dramatically promotedfrom viewpoints of both a car body structure and control. This causes asituation such that an engine sound cannot appropriately bring therealism of running.

Therefore, a sound effect (also referred to as an active engine sound)generation apparatus is proposed. The sound effect generation apparatusdetects driver's driving amount and generates, in a vehicle, a soundeffect of an engine according to the driving amount through anin-vehicle speaker.

A sound effect generation apparatus disclosed in Patent Literature 1includes fundamental frequency setting means for setting a fundamentalfrequency related to the number of cylinders and a rotation speed of anengine, harmonic determining means for determining a plurality ofharmonics of the fundamental frequency, and gain determining means fordetermining a harmonic-enhanced gain of the engine. The gain determiningmeans includes a circuit that determines an engine load. The engine loaddetermination circuit includes at least one of an accelerator pedalposition determination circuit, a mass airflow determination circuit, anegative pressure determination circuit, and an engine torquedetermination circuit. The engine load determination circuit adjusts aharmonic enhancing level based on the harmonic-enhanced gain.

This configuration causes vehicle occupants including a driver to feel astartlingly realistic engine sound.

Further, a vehicle control device disclosed in Patent Literature 2includes operation amount detecting means for detecting an operationamount of operation means to be operated during acceleration, transientoperation amount arithmetic means for calculating a transient operationamount based on a stationary state of the operation means, speedarithmetic means for calculating an operating speed of the operationmeans, and target arithmetic means for calculating at least one of atarget acceleration and a target sound pressure that increase by anincrease exceeding a differential threshold per time when a human canperceive stimuli received. At least one of a torque generation deviceand an in-vehicle acoustic device is controlled based on at least one ofthe target acceleration and the target sound pressure.

This configuration offers comfortable acceleration performance andacceleration feeling to a driver.

Normally, a sound recognized by a person is an auditory phenomenoncaused by a fluctuation (a sound wave) of an air pressure, and itsproperty is roughly classified into three parts including a volume, atone, and a timbre.

Herein, the volume is related to a sound pressure level, the tone isrelated to a frequency, and the timbre is related to a sound quality.

When a fundamental wave sound having a fundamental frequency componentand an integer-order component wave sound having an integer-order(secondary or more) frequency component with respect to the fundamentalwave sound are simultaneously generated, a concord in which both thesounds are mixed together is formed without a beat (interference)between the sounds because an integer-order adjustment wave sound (acomponent wave sound) of the integer-order frequency component is anovertone series of the fundamental wave sound.

On the contrary, when the fundamental wave sound and a component wavesound having a frequency component other than the integer-order(secondary or more) frequency component with respect to the fundamentalwave sound are simultaneously generated, a discord (an unclear sound) isgenerated by the interference between the sounds because an adjustmentwave sound to be synthesized with the fundamental wave sound is not anovertone series of the fundamental wave sound.

In the sound effect generation apparatus in Patent Literature 1, realismof an engine sound during actual running of a vehicle andcharacteristics of engine sounds that vary with vehicle types areartificially reproduced by setting a gain for enhancement per frequencycomponent wave sound.

Further, in the vehicle control device in Patent Literature 2, a soundeffect according to an increase in acceleration of a vehicle isgenerated by setting a target sound pressure level of a high-frequencycomponent wave sound of an engine sound.

However, in the sound effect generation apparatuses in Patent Literature1 and 2, since a harmonic-enhanced gain and a target sound pressurelevel are determined by using only an operation amount of an acceleratorpedal as a parameter, when a vehicle behavior and a sound effect do notmatch with each other, the sound effect is not congruent with a driver'swill and thus the driver might have a feeling of strangeness.

For example, when a vehicle moves on a road surface such as a frozenroad surface with a low road surface friction coefficient μ, even if adriver performs a steering operation, a turning operation is inhibited,and thus an actual turning amount of the vehicle is less than a steeringamount. Further, when the vehicle runs on an ascending road havingpredetermined gradient, even if the driver performs a steeringoperation, a turning operation is inhibited, and an actual turningamount of the vehicle is less than a steering amount.

That is, in the above condition (the inhibition condition) such that thecorrespondence between an amount of an operation performed by the driverand an actual vehicle behavior is inhibited, when the sound effectgeneration apparatus generates a sound effect corresponding to theamount of the operation by the driver although actual operability of thevehicle is degraded, the driver have a feeling of strangeness for thesound effect due to mismatch between the vehicle behavior and the soundeffect.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Translation of PCT Publication No.    2014-507679-   Patent Literature 2: Unexamined Japanese Patent Publication No.    2008-025492

SUMMARY OF INVENTION

An object of the present invention is to provide a vehicle sound effectgeneration apparatus that can eliminate a feeling of strangeness in anoperation performed by a vehicle occupant using acoustic presentationeffects regardless of an inhibition condition such that operability of avehicle is degraded.

The present invention for achieving the above object provides a vehiclesound effect generation apparatus for generating a sound effect of anengine based on a vibration sound database including a fundamental wavesound having a fundamental frequency component and a plurality ofadjustment wave sounds having a frequency component other than thefundamental frequency component, the vehicle sound effect generationapparatus including a running state detecting unit that detects arunning state of a vehicle, an adjustment wave sound selector thatselects one or more adjustment wave sounds having a half-order frequencycomponent or an integer-order frequency component, a sound effectgeneration unit that synthesizes the fundamental wave sound with the oneor more adjustment wave sounds selected by the adjustment wave soundselector, and an inhibition condition determining unit that candetermine a condition that correspondence between an amount of anoperation performed by a vehicle occupant and a behavior of the vehicleis inhibited, wherein when the inhibition condition determining unitdetermines the condition that the correspondence between an amount of anoperation performed by a vehicle occupant and a behavior of the vehicleis inhibited, the adjustment wave sound selector reduces outputcharacteristics of the one or more adjustment wave sounds selected.

The vehicle sound effect generation apparatus of the present inventioncan eliminate a feeling of strangeness in an operation performed by avehicle occupant using acoustic presentation effects regardless of aninhibition condition such that operability of a vehicle is degraded.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a vehicle equipped with avehicle sound effect generation apparatus according to a firstembodiment.

FIG. 2 is a block diagram of the vehicle sound effect generationapparatus.

FIG. 3 is a vibration sound map.

FIG. 4A to FIG. 4C illustrate gain maps of adjustment wave sounds set inaccordance with a lateral acceleration: FIG. 4A is a standard gain map;FIG. 4B is a decrease gain map; and FIG. 4C is an increase gain map.

FIG. 5 is a flowchart of a sound effect generating process.

FIG. 6 is a flowchart of a lateral input amount setting process.

FIG. 7 is a flowchart of a map selecting process.

FIG. 8 is a flowchart of a risk degree determining process.

FIG. 9 is a flowchart of a discord generating process.

FIG. 10 is a flowchart of a harmonic sound generating process.

FIG. 11 is a flowchart of a rumble sound generating process.

FIG. 12 is a flowchart of a weight setting process.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail belowwith reference to the drawings.

The following description illustrates that the present invention isapplied to a vehicle V, and does not limit the present invention, itsapplication, or its usefulness.

First Embodiment

A first embodiment of the present invention will be described below withreference to FIGS. 1 to 12.

A sound effect generation apparatus 1 selectively generates soundeffects (a harmonic sound, a rumble sound, and a discord) of an enginein accordance with a running state of the vehicle V, and differentlyuses tones of the sound effects of the engine in accordance with therunning state. As a result, the sound effect generation apparatus 1provides current and future running information to a driver (a vehicleoccupant) through an acoustic sense. In such a manner, an acousticpresentation effect during driving is heightened.

A sound effect presentation function provided by the sound effectgeneration apparatus 1 includes a realism enhancing function, a reminderfunction, and an operation uncomfortable feeling alleviating function.

Herein, the harmonic sound is a sound effect obtained by synthesizing afundamental wave sound having a fundamental frequency component with aninteger-order adjustment wave sound having an integer-order frequencycomponent of the fundamental wave sound. The rumble sound is a soundeffect obtained by synthesizing a fundamental wave sound having afundamental frequency component with a half-order adjustment wave soundhaving a half-order frequency component of the fundamental wave sound.The discord is a sound effect obtained by synthesizing a fundamentalwave sound having a fundamental frequency component with a discordantadjustment wave sound having a discordant frequency component other thanthe integer-order frequency component and the half-order frequencycomponent of the fundamental wave sound. Further, in the followingdescription, a primary frequency component is the fundamental frequencycomponent, and a primary component wave sound having the primaryfrequency component is the fundamental wave sound.

As illustrated in FIGS. 1 and 2, the sound effect generation apparatus 1includes an electric control unit (ECU) 2, a pair of right and leftspeakers 3 and 4 used as a part of an audio system, an acceleratorsensor 5, a yaw rate sensor 6, a steering angle sensor 7, a lateralacceleration sensor (hereinafter, referred to as a lateral G sensor) 8,a wheel speed sensor 9, a gradient sensor 10, a weight sensor 11, anavigation device 12, a turn control device (hereinafter, referred to asa DSC device) 13, a drive assist device 14, a mode selector switch 15,and the like.

The pair of speakers 3 and 4 is connected so as to be capable ofreceiving an electric signal from the ECU 2. The respective sensors 5 to11 and the mode selector switch 15 are connected so as to be capable oftransmitting an electric signal to the ECU 2. The respective devices 12to 14 are connected so as to be capable of transmitting and receiving anelectric signal to and from the ECU 2. At least one of the respectivesensors 5 to 11 and the respective devices 12 to 14 corresponds to arunning state detecting unit that directly or indirectly detects arunning state of the vehicle V including running environment informationof the vehicle V.

The pair of speakers 3 and 4 and the respective sensors 5 to 11 will befirst described.

The pair of speakers 3 and 4 is disposed on lower end portions of a pairof right and left front pillars, respectively, in accordance with a leftfront position and a right front position of a driver sat on a frontseat.

The speakers 3 and 4 are configured to be capable of independentlychanging respective frequency gains and sound pressure levels of sounds(sound effects) generated by an operation signal input from the ECU 2.

For this reason, when a sound pressure level of a sound effect generatedfrom the speaker 3 is set to be higher than a sound pressure level of asound effect generated from the speaker 4, a driver's visual line isguided toward the speaker 3. Therefore, the driver can be caused torecognize a left front visual field including a left door mirror.

Further, when a sound pressure level of a sound effect generated fromthe speaker 4 is set to be higher than a sound pressure level of a soundeffect generated from the speaker 3, a driver's visual line is guidedtoward the speaker 4. Therefore, the driver can be caused to recognize aright front visual field including a right door mirror.

The accelerator sensor 5 detects a pressing-down amount of anaccelerator pedal (not illustrated) and outputs a detection signal. Theyaw rate sensor 6 outputs a signal according to a yaw rate y of thevehicle V.

The steering angle sensor 7 outputs a signal relating to a steeringangle θ of a steering wheel operated by a driver. The lateral G sensor 8outputs a signal relating to a current lateral acceleration A which actson the vehicle V. The wheel speed sensor 9 outputs a signal according toa rotation speed of wheels (not illustrated) for detection of a vehiclespeed v. The gradient sensor 10 outputs a signal according to aninclination angle of a driving lane (road surface) on which the vehicleV currently runs or stops. The weight sensor 11 outputs a signalrelating to a weight of a load in a trunk of the vehicle V

The respective devices 12 to 14 will be described below.

As illustrated in FIGS. 1 and 2, the navigation device 12 is disposed onan upper center of an instrument panel, and includes a position detectorfor the vehicle V, a map data input unit, a sound output speaker, amonitor, and the like (they are not illustrated). The navigation device12 is electrically connected with a global positioning system (GPS)receiver (not illustrated) for detecting a current running position ofthe vehicle V.

The GPS receiver receives signals from a plurality of GPS satellites todetect a current position of the vehicle V.

Further, the navigation device 12 includes a map database in which roadmap data is stored, traffic rules database in which traffic rules datais stored, and the like (these databases are not illustrated).

As a result, the navigation device 12 gives a driver a route to driver'sdestination using the current position data of the vehicle V through theGPS receiver, the road map data in the map database, and the trafficrules data in the traffic rules database. The navigation device 12outputs the current position data of the vehicle V, the road map data,and the traffic rules data to the ECU 2.

The navigation device 12 corresponds to a turn information acquisitionunit that acquires curvature information including an existence positionand a turning radius of a curve on a driving lane in a traveling frontaldirection of the vehicle V from the map database.

The DSC device 13 receives input signals from the respective sensors toperform DSC control to improve running stability of the vehicle V duringturn.

Specifically, when determining, based on detection signals from the yawrate sensor 6, the lateral G sensor 8, and the wheel speed sensor 9,that a turning attitude of the vehicle V is lost by a predeterminedamount or more, the DSC device 13 controls braking forces of therespective wheels through an operation of a pressurizing unit (notillustrated) for a brake fluid pressure, and causes a yaw moment to acton a vehicle body so as to turn the turning attitude of the vehicle V ina target direction.

Further, the DSC device 13 receives the input signals from therespective sensors, and performs antilock brake system (ABS) control toprevent wheel locks of the respective wheels.

Specifically, the DSC device 13 calculates slip ratios of the respectivewheels based on a detection signal from the wheel speed sensor 9, andwhen detecting a wheel whose calculated slip ratio exceeds apredetermined threshold, controls the pressurizing unit to reduce thebraking force acting on the wheel detected. In such a manner, the wheellock is prevented.

The DSC device 13 calculates, based on a detection signal from thelateral G sensor 8 and a detection signal from the wheel speed sensor 9,a friction coefficient μ of the road surface (hereinafter, simply thefriction coefficient μ) as well as the slip ratios of the wheels, andoutputs the calculated friction coefficient μ to the ECU 2.

The drive assist device 14 has an inter-vehicle distance notifyingfunction of notifying an inter-vehicle distance in front of and behindthe vehicle V, a feeling improving function of improving driver'sfeeling, and the like.

The inter-vehicle distance notifying function is a function of avoidingcollision by sounding an alarm via the speakers 3 and 4 or lighting awarning lamp (not illustrated) so as to cause a driver to recognize arisk of collision when another vehicle (a leading vehicle or a followingvehicle) or an obstacle is present in a region which is separated fromthe vehicle V by a predetermined distance in front of and behind thevehicle V during running, and by guiding the driver to perform anavoiding operation.

The feeling improving function is a function of estimating a feelingrelating to driver's emotions during running, based on driver's facialexpression and action, and guiding a driver's feeling to an improvedzone (from an uncomfortable or inactive state to a comfortable or activestate) through lighting and music.

As illustrated in FIG. 1, the drive assist device 14 includes chargecoupled device (CCD) cameras 16 to 18 that can capture a still image ora moving image.

The front camera 16 is attached to a position near a rear-view mirror(not illustrated) on a front-end lower surface of a roof panel, and isconfigured to be capable of imaging a white line position of a drivinglane in a traveling frontal direction, a leading vehicle, approach andparting positions of a curve in the traveling frontal direction, and thelike, via a front windshield glass.

The rear camera 17 is attached to a rear-end lower surface of the roofpanel, and is configured to be capable of imaging a following vehicleand the like via a rear windshield glass. The cameras 16 and 17 are astereo type camera in which a lens mechanism and a shutter mechanism areshared by the two cameras, and are configured to be capable ofindividually detecting a distance between the vehicle V and an object tobe imaged and a direction from the vehicle V to the object to be imaged.

The indoor camera 18 is attached, for example, to above the instrumentpanel to image an upper body of the driver including a driver's face.The captured image of the upper body of the driver is used for:specifying a facial expression by cutting out the facial image from thecaptured image; specifying a dimension of pupils and an eye direction byenlarging and detecting irises of eyes; and specifying an attitude basedon a barycentric position of the image and a shape of the upper body,for example. A driver's emotion is estimated by using a biaxial planeformed by a transverse axis expressing comfort and discomfort and avertical axis expressing activeness and inactiveness (for example, aRussell's circumplex model of emotions) and a feature amount of adriver's facial expression imaged by the indoor camera 18.

Further, the indoor camera 18 can capture an indoor image including avehicle occupant (passenger) other than the driver at a wide angle, anddetects the number of vehicle occupants in the vehicle V through thiscaptured image.

The mode selector switch 15 includes a momentary selector switch withwhich activation (starting of an operation) of the sound effectgeneration apparatus 1 and a type (a mode) of a sound effect can beselected.

The mode selector switch 15 is configured to be capable of selecting afirst mode for generating an engine sound effect mainly including aharmonic sound through a predetermined ON operation, or a second modefor generating an engine sound effect mainly including a rumble soundthrough a predetermined ON operation.

All frequencies of component sounds match with each other and a beat(interference) does not occur between a fundamental wave sound and aninteger-order adjustment wave sound having an integer-order frequencycomponent. For this reason, a harmonic sound, which is obtained bysynthesizing the fundamental wave sound with one or more integer-orderadjustment wave sounds, reverberates, and a concord that makes a drivercomfortable is generated.

Interference partially occurs between a fundamental wave sound and ahalf-order adjustment wave sound, in which an even-number-order overtoneincludes a half-order frequency component which is an overtone series ofthe fundamental wave sound. However, since a driver (a vehicle occupant)feels such interference only slightly, a rumble sound, which is obtainedby synthesizing the fundamental wave sound with one or more half-orderadjustment wave sounds, is rather dynamic. Thus, a quasi-concord thatcauses the vehicle occupants such as the driver to recognize feeling ofpower is generated.

Further, when any one of the first and second modes is selected in an ONstate of the mode selector switch 15, a third mode for generating anengine sound effect mainly including a discord is executed under acondition that a risk degree B determined by a risk degree determiningunit 25, described later, is a determination threshold r1 or more fordetermining the risk degree.

The sound effect to be generated in the third mode is obtained bysynthesizing a fundamental wave sound having a fundamental frequencycomponent with one or more discordant adjustment wave sounds having adiscordant frequency component other than an integer-order frequencycomponent and a half-order frequency component of the fundamental wavesound. For this reason, a beat occurs between component sounds. Thus,this sound effect is a discord that gives the driver an uncomfortableimpression accompanied by nervousness and a sense of caution.

The ECU 2 will be described below.

The ECU 2 is configured to synthesize a fundamental wave sound with theselected one or more adjustment wave sounds to artificially generate anengine sound effect so as to improve a driver's operational feeling.

The ECU 2 includes a central processing unit (CPU), a read-only memory(ROM), a random-access memory (RAM), an amplifier, an in-side interface,and an out-side interface.

The ROM stores various programs and data for generating respectiveengine sound effects, and the RAM is provided with a processing area tobe used when the CPU executes a series of process.

The in-side interface is electrically connected to the respectivesensors 5 to 11, the respective devices 12 to 14, and the mode selectorswitch 15. The out-side interface is electrically connected to the pairof speakers 3 and 4 and the respective devices 12 to 14 via theamplifier.

The ECU 2 stores a vibration sound map M1 (a vibration sound database)in which a plurality of sound sources is stored, the sound sources beingpreset so as to be fitted to generated sounds from a four-cylindergasoline engine mounted to the vehicle V.

As illustrated in FIG. 3, the vibration sound map M1 stores, perrotation speed of an engine, sound sources at each unit frequency (forexample, 0.01-order frequency) from a primary component wave sound (afundamental wave sound) to 10-order component wave sound, the primarycomponent wave sound having a fundamental frequency component, the10-order component wave sound having a frequency component which is tentimes as large as the fundamental frequency component.

For this reason, the vibration sound map M1 includes, per rotation speedof an engine, a fundamental wave sound, an integer-order component wavesound (an integer-order adjustment wave sound) having a frequencycomponent which is an integral multiple of a fundamental frequencycomponent, a half-order component wave sound (a half-order adjustmentwave sound) in which an even-number-order overtone is an overtone seriesof the fundamental wave sound, and a discordant component wave sound (adiscordant adjustment wave sound) in which an overtone relationship doesnot hold with respect to the fundamental wave sound.

As illustrated in FIG. 2, the ECU 2 includes a lateral input amountsetting unit 21, an adjustment wave sound selector 22, a behavior delaypredicting unit 23, an inhibition condition determining unit 24, a riskdegree determining unit 25, a lateral G calculating unit 26 (a lateralacceleration calculating unit), a sound effect generation unit 27, and avisual guidance direction setting unit 28.

The lateral input amount setting unit 21 is configured to be capable ofsetting a lateral input amount P in which a physical amount relating toat least one of a movement of the vehicle V in a width direction and amovement of the vehicle V in the turning direction is a parameter, basedon a running state of the vehicle V detected by a running statedetecting unit (at least one of the respective sensors 5 to 11 and therespective devices 12 to 14).

When a detection value of a yaw rate is set to y and a detection valueof the lateral acceleration is set to A, in a case where the vehiclespeed v of the vehicle V is a determination threshold t2 or more, thelateral input amount P is calculated in accordance with a followingequation (1).

P=y/A   (1)

As a result, the lateral input amount P in which a sideslip tendency anda slip tendency of the vehicle V are reflected is obtained.

When the vehicle speed v of the vehicle V is less than the determinationthreshold t2, the lateral input amount setting unit 21 sets the lateralinput amount P to the lateral acceleration A. When the vehicle speed vis low like a time of turning right or left at an intersection, sincesideslip or slip of the vehicle V hardly occurs, the lateralacceleration A in which an actual turning state of the vehicle V isreflected most clearly is used as the lateral input amount P.

At least a vehicle state in a lateral direction may be reflected in thelateral input amount P. Like the lateral input amount P at thelow-vehicle speed, any one detection value of the steering angle θ ofthe steering wheel, the yaw rate y, and the lateral acceleration A maybe used as the lateral input amount P regardless of the vehicle speed v.Further, a parameter in which two or more detection values are combinedcan be adopted as the lateral input amount P regardless of the vehiclespeed v.

The adjustment wave sound selector 22 will be described below.

The adjustment wave sound selector 22 is configured to be capable ofselecting, from the plurality of component wave sounds stored in thevibration sound map M1, one or more adjustment wave sounds to besynthesized with a fundamental wave sound N0.

The adjustment wave sound selector 22 selects first to third adjustmentwave sounds N1 to N3, and determines, using the gain maps M2 to M4selected based on a running state, first to third gains g1 to g3(0<g1<g2<g3) for correcting the first to third adjustment wave sounds N1to N3, respectively.

These first to third gains g1 to g3 correspond to the outputcharacteristics of the first to third adjustment wave sounds N1 to N3.

The gain maps M2 to M4 will be described.

As illustrated in FIG. 4A to FIG. 4C, the ECU 2 stores a standard gainmap M2, a decrease gain map M3, an increase gain map M4 in advance.

Gains α2 to α4, β2 to β4, and γ2 to γ4 of the first to third adjustmentwave sounds N1 to N3 as one of output properties of a sound effect areset symmetrically so as to be defined to zero when the lateralacceleration A is zero and so as to be increased like a linear functionas an absolute value of the lateral acceleration A increases.

The gains α2 to α4, β2 to β4, and γ2 to γ4 increase at an increase ratewhich is larger than an increase rate before a certain mid-stage pointand are converged to a constant value at an upper limit value.

In the gain maps M2 to M4, the gain values are defined such that afollowing formula (2) holds.

γ2<β2<α2

γ3<β3<α3

γ4<β4<α4   (2)

Further, in the gain maps M2 to M4, the gain values are definedrespectively such that a following formula (3) holds.

α3<α2<α4

β3<β2<β4

γ3<γ2<γ4   (3)

The adjustment wave sound selector 22 selects the gain maps M2 to M4using, as determination conditions, a predicted result of the behaviordelay predicting unit 23 and a determined result of the inhibitioncondition determining unit 24.

The behavior delay predicting unit 23 is configured to predict that abehavior delay of the vehicle V occurs when a total weight of thevehicle V to be specified by the number of vehicle occupants and aweight of a cargo (hereinafter, simply a vehicle weight) is adetermination threshold t3 or more.

When the behavior delay predicting unit 23 predicts occurrence of thebehavior delay of the vehicle V in such a manner, the adjustment wavesound selector 22 selects the increase gain map M4 having highresponsivity.

That is, when the vehicle weight is the determination threshold t3 ormore, the behavior of the vehicle V is likely to be delayed with respectto a steering angle operation (an operation amount) performed by thedriver. For this reason, the adjustment wave sound selector 22 selectsthe increase gain map M4 having high responsivity such that a soundeffect is corrected to be increased prior to a current behavior of thevehicle V. As a result, the behavior delay of the vehicle V is correctedacoustically so that a driver's feeling of strangeness in the operationcan be eliminated.

The inhibition condition determining unit 24 is configured to determinethat the vehicle V is in a condition that association between a driver'soperation amount and the behavior of the vehicle V is inhibited, inother words, operability of the vehicle V is deteriorated (hereinafter,in the inhibition condition), when the friction coefficient μ is adetermination threshold t4 or less or when an ascending gradient is adetermination threshold t5 or more.

When the inhibition condition determining unit 24 determines theinhibition condition such that the operability of the vehicle V isdeteriorated, the adjustment wave sound selector 22 selects the decreasegain map M3 having low responsivity.

That is, when the friction coefficient μ input from the DSC device 13 isthe determination threshold t4 or less or when an ascending gradientinput from the gradient sensor 10 is the determination threshold t5 ormore, an actual behavior of the vehicle V can hardly follow a steeringangle operation performed by the driver. For this reason, the adjustmentwave sound selector 22 selects the decrease gain map M3 having lowresponsivity such that the sound effect is corrected to be decreased. Asa result, degradation of the following performance of the vehicle V iscorrected acoustically so that a driver's feeling of strangeness in theoperation can be eliminated.

On the other hand, when a behavior delay of the vehicle V and thedegradation of the following performance are unlikely to occur, thestandard gain map M2 having standard responsivity is selected.

Further, description returns to the adjustment wave sound selector 22.

When the first mode is selected, the adjustment wave sound selector 22is configured to select, based on the lateral input amount P, the firstto third adjustment wave sounds N1 to N3 having an integer-orderfrequency component.

Specifically, when the lateral input amount P is a determinationthreshold p2 or less (0<p1<p2), a secondary component wave sound whichis an integer-order frequency component closest to a fundamentalfrequency component is allocated to the first adjustment wave sound N1.When the lateral input amount P is larger than the determinationthreshold p2 and is a determination threshold p3 or less (p2<p3), atertiary component wave sound which is an integer-order frequencycomponent next closest after the secondary component wave sound isallocated to the second adjustment wave sound N2 as well as the alreadyselected first adjustment wave sound N1. When the lateral input amount Pis larger than the determination threshold p3, a quaternary componentwave sound which is an integer-order frequency component next closestafter the tertiary component wave sound is allocated to the thirdadjustment wave sound N3 as well as the already selected first andsecond adjustment wave sounds N1 and N2.

The reason for such an operation is that a consonance level of anadjustment wave sound having an integer-order frequency component can bemade to be higher as the integer-order frequency component is closer tothe fundamental frequency component.

The adjustment wave sound selector 22 extracts, based on the lateralinput amount P, the gain g1 (α2 to α4) for correcting the firstadjustment wave sound N1, the gain g2 (β2 to β4) for correcting thesecond adjustment wave sound N2, and the gain g3 (γ2 to γ4) forcorrecting the third adjustment wave sound N3 from any one of theselected gain maps M2 to M4. As described above, when the first mode isselected, as the lateral input amount P is larger, the adjustment wavesound selector 22 increases the number of the first to third adjustmentwave sounds N1 to N3 and increases the first to third gains g1 to g3 ofthe selected first to third adjustment wave sounds N1 to N3.

The adjustment wave sound selector 22 is configured to select, based onthe lateral input amount P, the first to third adjustment wave sounds N1to N3 having a half-order frequency component when the second mode isselected.

Specifically, when the lateral input amount P is the determinationthreshold p2 or less, a 1.5-order component wave sound which is ahalf-order frequency component closest to a fundamental frequencycomponent is allocated to the first adjustment wave sound N1. When thelateral input amount P is larger than the determination threshold p2 andis the determination threshold p3 or less, a 2.5-order component wavesound which is a half-order frequency component next closest after the1.5-order component wave sound is allocated to the second adjustmentwave sound N2 as well as the already selected first adjustment wavesound N1. When the lateral input amount P is larger than thedetermination threshold p3, a 3.5-order component wave sound which is ahalf-order frequency component next closest after the 2.5-ordercomponent wave sound is allocated to the third adjustment wave sound N3as well as the already selected first and second adjustment wave soundsN1 and N2.

The reason for such an operation is that a consonance level (aquasi-concordant level) of an adjustment wave sound having a half-orderfrequency component can be made to be higher as the half-order frequencycomponent is closer to the fundamental frequency component.

Similarly to the first mode, the adjustment wave sound selector 22extracts, based on the lateral input amount P, the gain g1 forcorrecting the first adjustment wave sound N1, the gain g2 forcorrecting the second adjustment wave sound N2, and the gain g3 forcorrecting the third adjustment wave sound N3 from any one of theselected gain maps M2 to M4. As described above, when the second mode isselected, as the lateral input amount P is larger, the adjustment wavesound selector 22 increases the number of the first to third adjustmentwave sounds N1 to N3 and increases the first to third gains g1 to g3 ofthe selected first to third adjustment wave sounds N1 to N3.

The adjustment wave sound selector 22 is configured to select, based onthe risk degree B, the first to third adjustment wave sounds N1 to N3having a discordant frequency component when the third mode is selectedin accordance with the determination in the risk degree determining unit25.

The risk degree determining unit 25 determines the risk degree B of thevehicle V based on a current running state.

The risk degree determining unit 25 calculates determination amounts ato c based on a steering angle speed Δθ in a driver's steeringoperation, the lateral input amount P, and an inter-vehicle distance Lbetween the vehicle V and a leading vehicle or a following vehicleclosest to the vehicle V, and calculates the risk degree B based on thecalculated determination amounts a to c.

When the steering angle speed Δθ is a determination threshold t6 ormore, the steering angle speed determination amount a is calculated inaccordance with a following formula (4). When the steering angle speedΔθ has the other values, the amount a is zero. Symbols k1 to k3 (0<k1,k2, k3) represent correction coefficients.

a=k1×Δθ  (4)

When the lateral input amount P is a determination threshold t7 or less,the lateral input amount determination amount b is calculated inaccordance with a following formula (5). When the lateral input amount Phas the other values, the amount b is zero.

b=k2×P   (5)

When the inter-vehicle distance L is a determination threshold t8 orless, the inter-vehicle distance determination amount c is calculated inaccordance with a following formula (6). When the inter-vehicle distanceL has the other values, the amount c is zero.

c=k3×L   (6)

The risk degree B is calculated in accordance with a following formula(7).

B=a+b+c   (7)

As a result, when each of the determination amounts is averagely highand also when a specific determination amount is high, the risk degree Bis determined accurately.

When the risk degree B determined by the risk degree determining unit 25is the determination threshold r1 or more (0<r1) in a state that eitherof the first and second modes is selected, the adjustment wave soundselector 22 determines that the third mode is selected and selects thefirst to third adjustment wave sounds N1 to N3 based on the risk degreeB.

Specifically, when the risk degree B is a determination threshold r2 orless (r1<r2), a 9.75-order component sound wave is allocated to thefirst adjustment wave sound N1, the 9.75-order component sound wavebeing a discordant frequency component which is farthest from thefundamental frequency component and is in a middle section between aninteger-order frequency component (a ten-order frequency component) anda half-order frequency component (a 9.5-order frequency component). Whenthe risk degree B is larger than the determination threshold r2 and is adetermination threshold r3 or less (r2<r3), a 9.25-order component soundwave is allocated to the second adjustment wave sound N2 as well as thealready selected first adjustment wave sound N1, the 9.25-ordercomponent sound wave being a discordant frequency component which isnext farthest from the fundamental frequency component after the9.75-order component sound wave and is in a middle section between aninteger-order frequency component (a 9-order frequency component) andthe half-order frequency component (the 9.5-order frequency component).When the risk degree B is larger than the determination threshold r3, a8.75-order component wave sound is allocated to the third adjustmentwave sound N3 as well as the already selected first and secondadjustment wave sounds N1 and N2, the 8.75-order component wave soundbeing a discordant frequency component which is next farthest fromfundamental frequency after the 9.25-order component sound wave and isin a middle section between the integer-order frequency component (the9-order frequency component) and a half-order frequency component (a8.5-order frequency component).

The reason for such an operation is that interference increases and adiscordant level can be made to be higher in the adjustment wave soundhaving the discordant frequency component as the discordant frequencycomponent is farther from the fundamental frequency component and isfarther from the integer-order frequency component and the half-orderfrequency component.

Similarly to the first and second modes, the adjustment wave soundselector 22 extracts, based on the lateral input amount P, the gain g1for correcting the first adjustment wave sound N1, the gain g2 forcorrecting the second adjustment wave sound N2, and the gain g3 forcorrecting the third adjustment wave sound N3 from any one of theselected gain maps M2 to M4, and corrects the first to third adjustmentwave sounds N1 to N3.

As described above, when the third mode is selected, as the risk degreeB is larger, the adjustment wave sound selector 22 increases the numberof the first to third adjustment wave sounds N1 to N3 to be selected andincreases the first to third gains g1 to g3 of the selected first tothird adjustment wave sounds N1 to N3.

When the prediction lateral acceleration A1 calculated by the lateral Gcalculating unit 25 is a determination threshold t1 or more, theadjustment wave sound selector 22 selects the first to third adjustmentwave sounds N1 to N3, and determines, using the gain maps M2 to M4selected based on the running state, the first to third gains g1 to g3for correcting the first to third adjustment wave sounds N1 to N3,respectively.

The lateral G calculating unit 26 is configured to determine, based onmap information including a turning radius input from the map databaseof the navigation device 12, whether a curve is present in the travelingfrontal direction of the vehicle V, and to calculate in advance, whenthe curve is present, the prediction lateral acceleration A1, which actson the vehicle V going around the curve.

The prediction lateral acceleration A1 is calculated under a conditionthat a curve is present at a distance which has been preset so as to beseparated from a current running position of the vehicle V or in an areawhere the vehicle V has been predicted to arrive within a preset time.

A turning angle θt of the wheels can be calculated in accordance with afollowing formula (8) when a prediction steering angle of the vehicle Vaccording to the turning radius of the curve is represented by θp and agear ratio of the vehicle V is represented by gr.

θt=θp/gr   (8)

Further, a front wheel position rotating radius R of the vehicle V canbe calculated in accordance with a following formula (9) when a wheelbase of the vehicle V is represented by W.

R=W/sin θt   (9)

When a vehicle speed is represented by v, the prediction lateralacceleration A1 can be expressed by a following formula (10). For thisreason, the prediction lateral acceleration A1, which acts on thevehicle V in going around the curve where the vehicle V runs in the nearfuture, can be obtained by assigning the front wheel position rotatingradius R calculated in accordance with the formula (9) to the formula(10).

A1=v ² /R   (10)

The sound effect generation unit 27 will be described below.

The sound effect generation unit 27 is configured to correct, asexpressed in a following formula (11), the first to third adjustmentwave sounds N1 to N3 respectively using the gains g1 to g3 extracted foreach mode, and synthesize the fundamental wave sound N0 with the firstto third adjustment wave sounds N1 to N3 corrected after selection togenerate a sound effect S.

N1←g1×N1

N2←g2×N2

N3←g3×N3   (11)

Further, the sound effect generation unit 27 increases a sound pressurelevel of the sound effect S as the lateral input amount P is larger, therisk degree B is larger, and the prediction lateral acceleration A1 islarger.

As a result, the driver is caused to acoustically recognize levels ofthe lateral input amount P, the risk degree B, and the predictionlateral acceleration A1 which affect running of the vehicle V.

The sound effect generation unit 27 is configured to be capable ofsetting the sound pressure level correction coefficients G_(L) and G_(R)of the pair of speakers 3 and 4 and changing the sound pressure levelsof the sound effects independently.

The sound effect generation unit 27 increases a sound pressure level ofthe speaker 3 (4) on a side of the visual guidance direction, the soundpressure level being set by the visual guidance direction setting unit28, and decreases a sound pressure level of the other speaker 4 (3) withrespect to a visual guidance direction θd.

When the visual line of the driver is guided, a strength ratio betweenthe sound pressure level correction coefficients G_(L) and G_(R) ischanged by setting the sound pressure level correction coefficientsG_(L) and G_(R) for correction coefficients k4 and k5, respectively, anda localized horizontal direction (position) of a sound image withrespect to a frontal direction of the driver is changed. In such amanner, a driver's attention (consciousness) is directed to thelocalized direction of the sound image.

The correction coefficients k4 and k5 are obtained as interpolationcoefficients to be set based on the visual guidance direction θd.

The visual guidance direction setting unit 28 is configured to determinepresence or absence of a visual guidance request based on variousinformation from the navigation device 12 and the drive assist device14, and be capable of setting, when the visual guidance request ispresent, the visual guidance direction θd at which the driver shoots alook in a frontal direction of the driver.

A subject at which the driver has to look is a subject that possiblyaffects running of the vehicle V from a viewpoint of safety andoperability when the driver does not recognize the subject. The visualguidance direction θd is defined as a direction where the driver canrecognize a subject at which the driver has to look with the driver as areference.

Specifically, in a situation that a following vehicle overtakes thevehicle V (or a vehicle that is running on a right lane is approachingrapidly), the following vehicle passes by on a right side of the vehicleV. For this reason, when the vehicle V makes a lane change to the rightlane, the vehicles might get contact with each other. Therefore, whenthe drive assist device 14 detects rapid approach of a following vehicle(a vehicle that is running on a right lane), the visual guidancedirection setting unit 28 determines presence of the visual guidancerequest to guide the driver's visual line to a right door mirror. Forthis reason, the visual guidance direction θd associated with a rightforward direction is set, and sound images of a sound effect (virtualsound source) from the speakers 3 and 4 are localized in the visualguidance direction θd.

Further, in a situation that the driver is following a curve, when adriver's visual line is not fixed to a parting position (or a clippingpoint) of the curve, the driver might lose control of the vehicle.Therefore, when the drive assist device 14 (the navigation device 12)detects a curve parting position during running, the visual guidancedirection setting unit 28 determines presence of the visual guidancerequest, and sets the visual guidance direction θd associated with acurve parting position to localize sound images of a sound effect fromthe speakers 3 and 4 in the visual guidance direction θd.

In a situation that the driver is tired during running on a freeway, thedriver might lose control of the vehicle. Therefore, when the driveassist device 14 detects a driver's fatigue (for example, uncomfortableand inactive) state, the visual guidance direction setting unit 28determines presence of the visual guidance request, and sets the visualguidance direction θd associated with a rest area (or an overhead sign)based on the map information in the navigation device 12 to localize thesound images of a sound effect from the speakers 3 and 4 in the visualguidance direction θd.

A procedure of a sound effect generating process will be described belowwith reference to flowcharts of FIGS. 5 to 12. In FIGS. 5 to 12, Si(i=1, 2 . . . ) represents a step of each process.

As illustrated in the flowchart of FIG. 5, in the sound effectgenerating process, first, in S1 various information such as detectionvalues of the respective sensors and determination thresholds is read,and the first to third adjustment wave sounds N1 to N3, the gains g1 tog3, a sound pressure level correction coefficient F, the sound pressurelevel correction coefficients G_(L) and G_(R), and the determinationamounts a to c which are set in the previous routine are initialized,and the process goes to S2.

In S2, a determination is made whether the mode selector switch 15 hasperformed an ON operation.

As a result of the determination in S2, when the mode selector switch 15has performed the ON operation, the process goes to S3 and a lateralinput amount setting process is executed. As the result of thedetermination in S2, when the mode selector switch 15 has not performedthe ON operation, the sound effect generating process is not executed,and the process returns.

After a map selecting process (S4) is executed, the process goes to S5and a risk degree determining process is executed.

In S6, a determination is made whether the risk degree B is thedetermination threshold r1 or more.

As a result of the determination in S6, when the risk degree B is thedetermination threshold r1 or more, the third mode is executed morepreferentially than the first and second modes. The process then goes toS7 and a discord generating process is executed.

The process goes to S8 and a weight setting process is executed.

The process then goes to S9. A signal of the left sound effect S_(L) isset by multiplying the sound effect S and the sound pressure levelcorrection coefficient G_(L), and a signal of the right sound effectS_(R) is set by multiplying the sound effect S and the sound pressurelevel correction coefficient G_(R).

The process then goes to S10. The control signals of the sound effectS_(L) and S_(R) are output to the speakers 3 and 4, respectively, andafter the sound effects S_(L) and S_(R) are generated from the speakers3 and 4, respectively, the process returns.

As the result of the determination in S6, when the risk degree B is lessthan the determination threshold r1, the process goes to S11, and adetermination is made whether a curve is present in the travelingfrontal direction of the vehicle V.

As a result of the determination in S11, when a curve is present in thetraveling frontal direction of the vehicle V, the process goes to S12,and the prediction lateral acceleration A1 is calculated by usingformulas (8) to (10).

In S13, a determination is made whether the prediction lateralacceleration A1 is the determination threshold t1 or more.

As a result of the determination in S13, when the prediction lateralacceleration A1 is the determination threshold t1 or more, a carefuldriving operation is necessary for running on a curve where the vehicleV enters in the near future, and an alert has to be raised such thatdriver's attention is turned to the driving operation. For this reason,the process goes to S14, and a multiplied value of the predictionlateral acceleration A1 by correction coefficient f1 is set as the soundpressure level correction coefficient F.

In S15, a determination is made whether the first mode has been selectedby an operation of the mode selector switch 15.

As a result of the determination in S15, when the first mode has beenselected, the process goes to S16. After the harmonic sound generatingprocess is executed, the process goes to S8.

As the result of the determination in S15, when the first mode has notbeen selected, the second mode is selected. For this reason, the processgoes to S17, and after the rumble sound generating process is executed,the process goes to S8.

As the result of the determination in S13, when the prediction lateralacceleration A1 is less than the determination threshold t1, theprediction lateral acceleration A1 to be generated in the future issmall, and the need to raise an alert for the driver is low. For thisreason, the process goes to S18, and a determination is made whether thecurrent lateral input amount P is a determination threshold p1 or more.

As a result of the determination in S18, when the lateral input amount Pis the determination threshold p1 or more, the lateral input amount Pthat affects a behavior of the vehicle V is generated. Therefore,process goes to S15.

As the result of the determination in S18, when the lateral input amountP is less than the determination threshold p1, the lateral input amountP that affects a behavior of the vehicle V is not generated. Therefore,process returns.

A procedure of the lateral input amount setting process will bedescribed below.

As illustrated in the flowchart of FIG. 6, in the lateral input amountsetting process, first, a determination is made in S21 whether thevehicle speed v is the determination threshold t2 or more.

As a result of the determination in S21, when the vehicle speed v is thedetermination threshold t2 or more, the process goes to S22, and a valueobtained by dividing the yaw rate y by the lateral acceleration A is setas the lateral input amount P. The process then ends.

As the result of the determination in S21, when the vehicle speed v isless than the determination threshold t2, the process goes to S23, andthe lateral acceleration A is set as the lateral input amount P. Theprocess then ends.

A procedure of the map selecting process will be described below.

As illustrated in the flowchart of FIG. 7, in the map selecting process,first, a determination is made in S31 whether a vehicle weight specifiedbased on the number of vehicle occupants and a weight of a cargo is thedetermination threshold t3 or more.

As a result of the determination in S31, when the vehicle weight is thedetermination threshold t3 or more, the behavior of the vehicle V mightbe delayed with respect to the steering angle operation performed by thedriver. For this reason, the process goes to S32, the increase gain mapM4 is selected, and then the process ends.

As the result of the determination in S31, when the vehicle weight isless than the determination threshold t3, the process goes to S33, and adetermination is made whether the friction coefficient μ is thedetermination threshold t4 or less, or the ascending gradient is thedetermination threshold t5 or more.

As a result of the determination in S33, when the friction coefficient μis the determination threshold t4 or less, or the ascending gradient isthe determination threshold t5 or more, an actual behavior of thevehicle V might hardly follow a steering angle operation performed bythe driver. For this reason, the process goes to S34, the decrease gainmap M3 is selected, and then the process ends.

As the result of the determination in S33, when the friction coefficientμ exceeds the determination threshold t4 and the ascending gradient isless than the determination threshold t5, an actual behavior of thevehicle V follows a steering angle operation performed by the driver.Therefore, the process goes to S35, the standard gain map M2 isselected, and then the process ends.

A procedure of the risk degree determining process will be describedbelow.

As illustrated in the flowchart of FIG. 8, in the risk degreedetermining process, first, a determination is made in S41 whether thesteering angle speed Δθ is the determination threshold t6 or more.

As a result of the determination in S41, when the steering angle speedΔθ is the determination threshold t6 or more, the process goes to S42.Thereafter, a multiplied value of the steering angle speed Δθ by thecorrection coefficient k1 is set as the steering angle speeddetermination amount a.

In S43, a determination is made whether the lateral input amount P isthe determination threshold t7 or less.

As a result of the determination in S43, when the lateral input amount Pis the determination threshold t7 or less, the process goes to S44 and amultiplied value of the lateral input amount P by the correctioncoefficient k2 is set as the lateral input amount determination amountb.

In S45, a determination is made whether the inter-vehicle distance Lwith respect to a leading vehicle or a following vehicle is thedetermination threshold t8 or less.

As a result of the determination in S45, when the inter-vehicle distanceL is the determination threshold t8 or less, the process goes to S46,and a multiplied value of the inter-vehicle distance L by the correctioncoefficient k3 is set as the inter-vehicle distance determination amountc.

In S47, a value obtained by adding the determination amounts a, b, and cis set as the risk degree B, and then the process ends.

As the result of the determination in S45, when the inter-vehicledistance L exceeds the determination threshold t8, the process goes toS48, and the inter-vehicle distance determination amount c is set tozero. The process then goes to S47.

As the result of the determination in S43, when the lateral input amountP exceeds the determination threshold t7, the process goes to S49, andthe lateral input amount determination amount b is set to zero. Theprocess then goes to S45.

As the result of the determination in S41, when the steering angle speedΔθ is less than the determination threshold t6, the process goes to S50,and the steering angle speed determination amount a is set to zero. Theprocess then goes to S43.

A procedure of the discord generating process will be described below.

As illustrated in a flowchart of FIG. 9, in the discord generatingprocess, first, a determination is made in S51 whether the risk degree Bis the determination threshold r2 or less.

As a result of the determination in S51, when the risk degree B is thedetermination threshold r2 or less, the risk degree B is at anintermediate level, and thus the process goes to S52.

In S52, the 9.75-order component sound wave which is the discordantfrequency component is set to the first adjustment wave sound N1, andthe process goes to S53 without setting the second and third adjustmentwave sounds N2 and N3 (in this case, N2 and N3 are zero, the samebelow).

In S53, the gain g1 (g2, g3) of the adjustment wave sound N1 (N2, N3)set in the previous step is set based on the gain map selected in themap selecting process.

The process then goes to S54, and a multiplied value of the risk degreeB by a correction coefficient f2 is set as the sound pressure levelcorrection coefficient F.

In S55, a multiplied value, which is obtained by multiplying an addedvalue of the first adjustment wave sound N1 corrected by the gain g1,the second adjustment wave sound N2 corrected by the gain g2, and thethird adjustment wave sound N3 corrected by the gain g3, by the soundpressure level correction coefficient F, is set to the sound effect S.The process then ends.

As the result of the determination in S51, when the risk degree Bexceeds the determination threshold r2, the process goes to S56, and adetermination is made whether the risk degree B is the determinationthreshold r3 or less.

As a result of the determination in S56, when the risk degree B is thedetermination threshold r3 or less, the risk degree B is large.Therefore, the process goes to S57.

In S57, the 9.75-order component sound wave is set to the firstadjustment wave sound N1, and the 9.25-order component sound wave whichis discordant frequency component is set to the second adjustment wavesound N2. The process goes to S53 without setting the third adjustmentwave sound N3.

As the result of the determination in S56, when the risk degree Bexceeds the determination threshold r3, the risk degree B is extremelylarge, and thus the process goes to S58.

In S58, the 9.75-order component sound wave is set to the firstadjustment wave sound N1, the 9.25-order component sound wave is set tothe second adjustment wave sound N2, and the 8.75-order component wavesound which is the discordant frequency component is set to the thirdadjustment wave sound N3. Thereafter, the process goes to S53.

A procedure of the harmonic sound generating process will be describedbelow.

As illustrated in the flowchart of FIG. 10, in the harmonic soundgenerating process, first, a determination is made in S61 whether thelateral input amount P is the determination threshold p2 or less.

As a result of the determination in S61, when the lateral input amount Pis the determination threshold p2 or less, the lateral input amount P isat an intermediate level, and thus the process goes to S62.

In S62, the secondary component wave sound which is the integer-orderfrequency component is set to the first adjustment wave sound N1, andthe process goes to S63 without setting the second and third adjustmentwave sounds N2 and N3.

In S63, the gain g1 (g2, g3) of the adjustment wave sound N1 (N2, N3)set in the previous step is set based on the gain map selected in themap selecting process.

The process then goes to S64, and a determination is made whether thesound pressure level correction coefficient F has already been set.

As a result of the determination in S64, when the sound pressure levelcorrection coefficient F has already been set, the process goes to S65.

In S65, a multiplied value, which is obtained by multiplying an addedvalue of the first adjustment wave sound N1 corrected by the gain g1,the second adjustment wave sound N2 corrected by the gain g2, and thethird adjustment wave sound N3 corrected by the gain g3, by the soundpressure level correction coefficient F, is set to the sound effect S.The process then ends.

As the result of the determination in S64, when the sound pressure levelcorrection coefficient F has not yet been set, the process goes to S66.

In S66, a multiplied value of the lateral input amount P by a correctioncoefficient f3 is set as the sound pressure level correction coefficientF, and then the process goes to S65.

As the result of the determination in S61, when the lateral input amountP exceeds the determination threshold p2, the process goes to S67. Adetermination is made whether the lateral input amount P is thedetermination threshold p3 or less.

As a result of the determination in S67, when the lateral input amount Pis the determination threshold p3 or less, the lateral input amount P islarge, and thus the process goes to S68.

In S68, the secondary component wave sound is set to the firstadjustment wave sound N1, and the tertiary component wave sound which isthe integer-order frequency component is set to the second adjustmentwave sound N2. The process goes to S63 without setting the thirdadjustment wave sound N3.

As the result of the determination in S67, when the lateral input amountP exceeds the determination threshold p3, the lateral input amount P isextremely large, and thus the process goes to S69.

In S69, the secondary component wave sound is set to the firstadjustment wave sound N1, the tertiary component wave sound is set tothe second adjustment wave sound N2, and the quaternary component wavesound N which is the integer-order frequency component is set to thethird adjustment wave sound N3. The process then goes to S63.

A procedure of the rumble sound generating process will be describedbelow.

As illustrated in the flowchart of FIG. 11, in the rumble soundgenerating process, first, a determination is made in S71 whether thelateral input amount P is the determination threshold p2 or less.

As a result of the determination in S71, when the lateral input amount Pis the determination threshold p2 or less, the lateral input amount P isat an intermediate level, and thus the process goes to S72.

In S72, the 1.5-order component wave sound which is the half-orderfrequency component is set to the first adjustment wave sound N1, andthe process goes to S73 without setting the second and third adjustmentwave sounds N2 and N3.

In S73, the gain g1 (g2, g3) of the adjustment wave sound N1 (N2, N3)set in the previous step is set based on the gain map selected in themap selecting process.

The process then goes to S74, and a determination is made whether thesound pressure level correction coefficient F has already been set.

As a result of the determination in S74, when the sound pressure levelcorrection coefficient F has already been set, the process goes to S75.

In S75, a multiplied value, which is obtained by multiplying an addedvalue of the first adjustment wave sound N1 corrected by the gain g1,the second adjustment wave sound N2 corrected by the gain g2, and thethird adjustment wave sound N3 corrected by the gain g3, by the soundpressure level correction coefficient F, is set to the sound effect S.The process then ends.

As the result of the determination in S74, when the sound pressure levelcorrection coefficient F has not yet been set, the process goes to S76.

In S76, a multiplied value of the lateral input amount P by a correctioncoefficient f4 is set as the sound pressure level correction coefficientF, and then the process goes to S65.

As the result of the determination in S71, when the lateral input amountP exceeds the determination threshold p2, the process goes to S77 and adetermination is made whether the lateral input amount P is thedetermination threshold p3 or less.

As a result of the determination in S77, when the lateral input amount Pis the determination threshold p3 or less, the lateral input amount P islarge, and thus the process goes to S78.

In S78, the 1.5-order component wave sound is set to the firstadjustment wave sound N1, the 2.5-order component wave sound which isthe half-order frequency component is set to the second adjustment wavesound N2. The process then goes to S73 without setting the thirdadjustment wave sound N3.

As the result of the determination in S77, when the lateral input amountP exceeds the determination threshold p3, the lateral input amount P isextremely large, and thus the process goes to S79.

In S79, the 1.5-order component wave sound is set to the firstadjustment wave sound N1, the 2.5-order component wave sound is set tothe second adjustment wave sound N2, and the 3.5-order component wavesound which is the half-order frequency component is set to the thirdadjustment wave sound N3. The process then goes to S73.

A procedure of the weight setting process will be described below.

As illustrated in the flowchart of FIG. 12, in the weight settingprocess, first, the visual guidance direction setting unit 28 determinesin S81 whether the visual guidance request is present.

As a result of the determination in S81, when the visual guidancerequest is present, the sound pressure levels of the right and leftspeakers 3 and 4 are necessarily differentiated. Therefore, the processgoes to S82 and the visual guidance direction θd is set.

The process then goes to S83, and the sound pressure level correctioncoefficients G_(L) and G_(R) are set to the correction coefficients k4and k5, respectively, based on the visual guidance direction θd.Thereafter, the process ends.

As the result of the determination in S81, when the visual guidancerequest is not present, the sound pressure levels of the right and leftspeakers 3 and 4 are not necessarily differentiated. Therefore, thesound pressure level correction coefficients G_(L) and G_(R) are set to1, and the process ends.

A function and an effect of the vehicle sound effect generationapparatus 1 will be described below.

The sound effect generation apparatus 1 includes sensors 6, 8 and thelike that detect a running state of the vehicle V, the adjustment wavesound selector 22 that selects the first to third adjustment wave soundsN1 to N3 including a half-order frequency component or an integer-orderfrequency component, and the sound effect generation unit 27 thatsynthesizes the fundamental wave sound N0 with the selected first tothird adjustment wave sounds N1 to N3. Therefore, the sound effect S canbe generated, based on an actual running behavior of the vehicle V, by aharmonic sound or a rumble sound that does not make the driveruncomfortable.

Further, the sound effect generation apparatus 1 includes the inhibitioncondition determining unit 24 that can determine a condition that thecorrespondence between an amount of an operation performed by a driverand a behavior of the vehicle V is inhibited. Therefore, the inhibitioncondition determining unit 24 can determine occurrence of an inhibitioncondition such that the behavior of the vehicle V does not follow theamount of the operation to be performed by the driver. When theinhibition condition determining unit 24 determines occurrence of aninhibition condition, the adjustment wave sound selector 22 reduces theoutput characteristics of the selected first to third adjustment wavesounds N1 to N3. For this reason, the driver can acoustically adjust andrecognize a behavior of the vehicle V and the sound effect S (S_(L),S_(R)) so as to be capable of avoiding the occurrence of a feeling ofstrangeness in the operation.

The adjustment wave sound selector 22 reduces the gains g1 to g3 of theadjustment wave sounds N1 to N3 as output characteristics of the firstto third adjustment wave sounds N1 to N3. For this reason, a behavior ofthe vehicle V and the sound effect S can be adjusted with a simpleconfiguration.

The inhibition condition determining unit 24 determines that thecorrespondence between the amount of an operation performed by thedriver and behavior of the vehicle V is inhibited at a time of runningon a road surface with the low friction coefficient μ (low μ road) or anascending road. For this reason, a feeling of strangeness in theoperation, which might occur at the time of running on the low μ road oron the ascending road can be securely avoided.

The sound effect generation apparatus 1 includes the lateral inputamount setting unit 21 that sets, based on the running state detected bythe sensors 6, 8 and the like, the lateral input amount P in which aphysical amount relating to at least one of a movement of the vehicle Vin the width direction and a movement of the vehicle V in the turningdirection is a parameter. The sound effect generation unit 27synthesizes the fundamental wave sound N0 with the first to thirdadjustment wave sounds N1 to N3 based on the lateral input amount P. Forthis reason, the occurrence of a feeling of strangeness in the operationis avoided and simultaneously the lateral input amount P in which anactual turning behavior of the vehicle V is reflected can be set.Therefore, the sound effect S adaptable to the actual turning behaviorof the vehicle V can be generated.

A modified example in which the embodiment is partially changed will bedescribed below.

[1] In the above embodiment, the number of adjustment wave sounds to besynthesized with a fundamental wave sound can be set to at most 3 basedon a running state, but the number of the adjustment wave sounds may beset to 2 or 4 or more according to a specification, a runningenvironment, and a state of the vehicle V. When the number of adjustmentwave sounds is set to 4 or more, the number of gains defined in the gainmaps M2 to M4 is preferably set according to the number of setadjustment wave sounds.

[2] The above embodiment has described an example where the inhibitioncondition determining unit determines an inhibition condition based onthe friction coefficient μ or the ascending gradient. However, theinhibition condition determining unit may determine at least a conditionthat correspondence between an amount of an operation performed by adriver and a behavior of the vehicle is inhibited, and thus maydetermine road surface factors other than the friction coefficient μ orthe ascending gradient. Further, the inhibition condition determiningunit can determine also vehicle factors relating to vehicle performancesand factors of a vehicle occupant relating to occupant's healthconditions as well as the road surface factors.

[3] In the above embodiment, the sound effect generation unit changesthe sound pressure levels of the pair of right and left speakers so thatthe localized direction of a sound image is changed. However, thelocalized direction of a sound image may be changed by setting a delaytime of a sound effect to reach the driver while the sound pressurelevels of the pair of speakers are maintained without changing the soundpressure levels of the pair of speakers.

Specifically, an output from the speaker on a side opposite to thevisual guidance direction is delayed from an output from the visualguidance direction-side speaker, so that the localized direction of asound image can be moved toward the visual guidance direction.

Further, in order to heighten recognition by the driver, the localizeddirection of a sound image may be shifted linearly from the frontaldirection of the driver through the visual guidance direction, and thisshifting operation may be repeated.

Further, speakers may be movable. In addition to the pair of speakers, aspeaker may be additionally disposed above the pair of speakers so thatthe visual guidance direction can be set three-dimensionally.

[4] The above embodiment has described an example of the drive assistdevice having the inter-vehicle distance notifying function and thefeeling improving function. However, the drive assist device can detectat least an outside-vehicle situation and an in-vehicle situation, andthus may have an obstacle detecting function or a white line (of adriving lane) detecting function.

Further, detecting means may be means other than a CCD, and thus may be,for example, a millimeter-wave radar.

[5] The above embodiment has described an example in which the soundeffect generation apparatus that generates a sound effect of an enginebased on a lateral input amount is used in combination. However, thesound effect generation apparatus just has to reduce outputcharacteristics of a sound effect in at least an inhibition condition.Therefore, a sound effect generation apparatus that generates a soundeffect of an engine based on an accelerator opening degree may be usedin combination. When an engine sound effect is generated based on theaccelerator opening degree, one integer or half-order adjustment wavesound or a plurality of integer or half-order adjustment wave sounds andtheir gains are set based on the accelerator opening degree. Further,control is made such that the number of adjustment wave sounds to besynthesized with the fundamental wave sound, gain values for correctingthese adjustment wave sounds, and a sound pressure level of a soundeffect increase as the accelerator opening degree is larger.

[6] The above embodiment has described an example where the vibrationsound map is used. However, a vibration sound map may be prepared foreach engine specification such as displacement or the number ofcylinders so that a vibration sound map according to an enginespecification can be selected when a mounted engine is replaced.

The above embodiment has described an example using the vibration soundmap of the four-cylinder gasoline engine actually mounted to a vehicle.However, a sound effect may be generated by using a vibration sound mapof any internal combustion (for example, a four-cylinder gasolineengine) for a hybrid vehicle or an electric vehicle.

[7] The above embodiment has described an example where the DSC deviceand the gradient sensor that detect the friction coefficient μ and theascending gradient, respectively, are provided. However, these factorsmay be obtained from a navigation device.

[8] Embodiments obtained by applying various modifications of which aperson skilled in the art thinks to the embodiments may be includedwithin a range of the present invention as long as they do not deviatefrom the subject matter of the present invention.

Summary of the Embodiment

The above embodiment will be summarized as follows.

The above embodiment relates to a vehicle sound effect generationapparatus for generating a sound effect of an engine based on avibration sound database including a fundamental wave sound having afundamental frequency component and a plurality of adjustment wavesounds having a frequency component other than the fundamental frequencycomponent. The vehicle sound effect generation apparatus includes therunning state detecting unit that detects a running state of a vehicle,the adjustment wave sound selector that selects one or more adjustmentwave sounds having a half-order frequency component or an integer-orderfrequency component, the sound effect generation unit that synthesizesthe fundamental wave sound with the one or more adjustment wave soundsselected by the adjustment wave sound selector, and the inhibitioncondition determining unit that can detect the condition that thecorrespondence between the amount of the operation performed by thevehicle occupant and the behavior of the vehicle is inhibited. When theinhibition condition determining unit determines the condition that thecorrespondence between the amount of the operation performed by thevehicle occupant and the behavior of the vehicle is inhibited, theadjustment wave sound selector reduces the output characteristics of theadjustment wave sounds selected.

The vehicle sound effect generation apparatus includes the running statedetecting unit that detects a running state of a vehicle, the adjustmentwave sound selector that selects one or more adjustment wave soundshaving a half-order frequency component or an integer-order frequencycomponent, and the sound effect generation unit that synthesizes thefundamental wave sound with the one or more adjustment wave soundsselected by the adjustment wave sound selector. For this reason, thesound effect can be generated, based on the actual running behavior ofthe vehicle, by a harmonic sound or a rumble sound that does not makethe vehicle occupant uncomfortable.

Further, the vehicle sound effect generation apparatus includes theinhibition condition determining unit that can determine the conditionthat the correspondence between the amount of the operation performed bythe vehicle occupant and the behavior of the vehicle is inhibited. Forthis reason, it is possible to determine occurrence of an inhibitioncondition such that the behavior of the vehicle does not follow theamount of the operation performed by the vehicle occupant. When theinhibition condition determining unit determines the occurrence of theinhibition condition, the adjustment wave sound selector reduces theoutput characteristics of the one or more adjustment wave soundsselected. For this reason, the vehicle occupant can acoustically adjustand recognize a behavior of the vehicle and the sound effect so as to becapable of avoiding the occurrence of a feeling of strangeness in theoperation.

Preferably, the output characteristics are a gain or gains of the one ormore adjustment wave sounds.

With this configuration, a behavior of the vehicle and a sound effectcan be adjusted with the simple configuration.

Preferably, the condition that the correspondence between the amount ofthe operation operated by the vehicle occupant and the behavior of thevehicle is inhibited is a condition that the vehicle runs on a road witha low friction coefficient (low μ road) or on an ascending road.

With this configuration, a feeling of strangeness in the operation whichmight occur at a time of running on a low μ road or an ascending roadcan be securely avoided.

Preferably, the vehicle sound effect generation apparatus furtherincludes a lateral input amount setting unit that sets, based on therunning state detected by the running state detecting unit, a lateralinput amount in which a physical amount relating to at least one of amovement of the vehicle in a width direction and a movement of thevehicle in a turning direction is a parameter, in which the sound effectgeneration unit synthesizes the fundamental wave sound with theadjustment wave sounds based on the lateral input amount.

With this configuration, the occurrence of a feeling of strangeness inthe operation is avoided, and simultaneously the lateral input amount inwhich an actual turning behavior of the vehicle is reflected can be set,and thus the sound effect adaptable to the actual turning behavior ofthe vehicle can be generated.

1. A vehicle sound effect generation apparatus for generating a soundeffect of an engine based on a vibration sound database including afundamental wave sound having a fundamental frequency component and aplurality of adjustment wave sounds having a frequency component otherthan the fundamental frequency component, the vehicle sound effectgeneration apparatus comprising: a running state detecting unit thatdetects a running state of a vehicle; an adjustment wave sound selectorthat selects one or more adjustment wave sounds having a half-orderfrequency component or an integer-order frequency component; a soundeffect generation unit that synthesizes the fundamental wave sound withthe one or more adjustment wave sounds selected by the adjustment wavesound selector; and an inhibition condition determining unit that candetermine a condition that correspondence between an amount of anoperation performed by a vehicle occupant and a behavior of the vehicleis inhibited, wherein when the inhibition condition determining unitdetermines the condition that the correspondence between the amount ofthe operation performed by the vehicle occupant and the behavior of thevehicle is inhibited, the adjustment wave sound selector reduces outputcharacteristics of the one or more adjustment wave sounds selected. 2.The vehicle sound effect generation apparatus according to claim 1,wherein the output characteristics are a gain or gains of the one ormore adjustment wave sounds.
 3. The vehicle sound effect generationapparatus according to claim 1, wherein the condition that thecorrespondence between the amount of the operation performed by thevehicle occupant and the behavior of the vehicle is inhibited is acondition that the vehicle runs on a road with a low frictioncoefficient or on an ascending road.
 4. The vehicle sound effectgeneration apparatus according to claim 1, further comprising a lateralinput amount setting unit that sets, based on the running state detectedby the running state detecting unit, a lateral input amount in which aphysical amount relating to at least one of a movement of the vehicle ina width direction and a movement of the vehicle in a turning directionis a parameter, wherein the sound effect generation unit synthesizes thefundamental wave sound with the one or more adjustment wave sounds basedon the lateral input amount.